_HOMEBREW My LED Heirloom Clock _{By Blake Hannaford}

In the summer of 1975, I had just

completed a rigorous course in digital logic design and decided to build an LED clock to last the rest of my life. To start, I partitioned the design into three printed circuit boards: display, clock logic, and power supply. I bought copper-plated boards and ferric chloride at RadioShack, signed each card with my name and the date, and etched out the boards in the backyard of my parents’ house. I bought discrete red LEDs from a surplus dealer; two green LEDs made the blinking colon between hours and minutes. The shop manager at Chicago’s Institute of Design helped me cut out the plexiglass pieces for the case on a table saw. The clock’s design mirrors Mies van der Rohe’s famous Crown Hall, the building in which it took shape. I ordered the MM5313 clock chip (the closest analogy today to the power of that chip would be building your own 60GB video iPod) and power supply parts and was off to the races.

Since then, the clock’s little green colon has blinked almost a billion times. The fuse I installed for safety has never blown; the capacitors in the power supply still seem to be fine. Nothing inside its plexiglass walls

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ever changes. Every three to five years, some of the segments begin to dim, so I remove the display board and clean the copper pads with just a pencil eraser.

Sometimes all that is required to keep the clock running smoothly is to pick it up a couple of inches and drop it. We all have our favorite old pieces of retro electronics, but how many have been powered up and working almost continuously for 31 years?

I recently came into possession of my family’s heirloom grandfather clock. The owners of the clock have signed their names inside the front door in pencil, starting with John Gates, who built the clock in the early 1800s. I don’t know anything about him, but presumably he bought the mechanism and built the clock with hand tools out in his barn — a process not really all that different from my own. I doubt that my clock will serve as long as the grandfather clock has, but the lesson is clear: when doing your next project, put your heart into it. Design it to last. Build it well. You will be glad you did.

Blake Hannaford directs the Biorobotics Lab at the University of Washington, Seattle.

Photograph by Blake Hannaford